Simulation of sputtering from ion-beam-roughened carbon surfaces

Effects of ion-induced surface roughness on sputtering of amorphous carbon under ion bombardment are studied by means of binary-collision computer simulation in a wide range of incidence angles. Most simulations refer to 1–10?keV Ar ion bombardment, and sinusoidal ripple morphology is assumed. It is shown that surface roughness is a key factor to achieve quantitative agreement with experiment. The simulation results are compared with the analytical estimates of the yield from sine-shaped and ridged surfaces based on continuum models of ion sputtering. Some deviations between the results are discussed.     

Study of the physical sputtering of a carbon-ceramic composite by ion bombardment

The results of experimental study and computer simulation of SG-P-0.1 carbon-ceramic composite sputtering under 30 keV Ar⁺ ion irradiation at normal incidence are presented. A comparison with the simulation data shows that taking into account the nanometric wave-like relief well describes an approximately threefold increase in the sputtering yield observed in the experiment in comparison to the smooth surface calculation.     

Simulation of radiation damage in materials under high fluence ion bombardment

The results of analytical estimations and computer simulation of a radiation damage level dpa are presented and discussed taking into account the material sputtering under ion bombardment. It is shown that the calculations of a stationary level of radiation damage are necessary for the interpretation of regularities of a radiation damage in materials under high fluence ion bombardment.     

Interpretation of TOF–SIMS depth profiles from ultrashallow high-k dielectric stacks assisted by hybrid collisional computer simulation

The TRIDYN collisional computer simulation has been modified to account for emission of ionic species and molecules during sputter depth profiling, by introducing a power law dependence of the ion yield as a function of the oxygen surface concentration and by modelling the sputtering of monoxide molecules. The results are compared to experimental data obtained with dual beam TOF–SIMS depth profiling of ZrO₂/SiO₂/Si high-k dielectric stacks with thicknesses of the SiO₂ interlayer of 0.5, 1, and 1.5 nm. Reasonable agreement between the experiment and the computer simulation is obtained for most of the experimental features, demonstrating the effects of ion-induced atomic relocation, i.e., atomic mixing and recoil implantation, and preferential sputtering. The depth scale of the obtained profiles is significantly distorted by recoil implantation and the depth-dependent ionization factor. A pronounced double-peak structure in the experimental profiles related to Zr is not explained by the computer simulation, and is attributed to ion-induced bond breaking and diffusion, followed by a decoration of the interfaces by either mobile Zr or O. PACS 68.49; 79.20; 81.65; 82.80     

Cone shape evolution under ion bombardment

The evolution of the profile of a cone developing under ion bombardment on the etch pit bottom has been investigated by computer simulation taking into account sputtering and ion-induced migration of atoms. A twofold increase in the cone apex angle is observed, which is accompanied by the appearance of kinks on its generatrix. A plateau arises on the pit bottom and a circular parapet is formed above the flat surface.     

Some of the current trends in the studies of sputtering

Abstract

The main directions in experimental, theoretical and computer studies of sputtering of solids under ion bombardment are analyzed. It is emphasized that there is a close relation between these studies and practical applications of sputtering.     

Simulation of boron nitride sputtering process and its comparisonwith experimental data

In the paper, TRIM and TRIDYN simulation codes were used to simulate the sputtering processes of boron nitride (BN) films during bombardment of ions. The TRIM and TRIDYN codes are applicable to the simulation of sputtering processes of different target materials with amorphous and polycrystalline structure. The results of the simulations are compared with experimental data. The sputtering experiments of polycrystalline hexagonal BN (h-BN) and cubic BN (c-BN) films were performed in a Commonwealth Scientific Corporation (CSC) 38-cm ion beam source device. The comparison of calculated and experimental results indicated that a) the experimental sputtering yields of h-BN and c-BN films bombarded with Ar⁺ ions versus the angle of incidence are in reasonable agreement with the calculated results; b) the sputtering yields of h-BN and c-BN bombarded with Ar⁺ are nearly of the same values versus the angle of incidence-preferential sputtering of h-BN was not found; c) the calculated sputtering. Yields of BN as a function of Ar⁺ ion energy are very sensitive to values of the surface binding energy (SEE); and d) surface binding energy between 2 and 3 eV for BN appears to be reasonable for the simulation of sputtering process of h-BN and c-BN films     

Sputtering of boron nitride single crystals of different structure

Results obtained in studying the sputtering of single crystals of hexagonal, rhombohedral, and cubic boron nitride modifications by computer simulations are reported. Data on sputtering the (0001) face of BN in two graphite-like modifications and the (111) face of BN crystals with a cubic lattice are presented. The energy and angular dependences of the sputtering yields and spatial and energy distributions of sputtered particles are considered for the cases of normal and oblique ion incidence. Specific features of the anisotropy of spatial distributions of sputtered particles and mechanisms of their formations are analyzed.     

The influence of surface diffusion on the results of surface analysis — a model calculation

The influence of surface diffusion on some results of surface-analytical methods using sputtering is investigated by computer simulation of the combined effect of sputtering and surface diffusion on a model “crystal” consisting of one monolayer of some species on top of a semiinfinite inert matrix. The computations show that surface diffusion is able to cause erroneous results under “typical” experimental conditions. Criteria are given to avoid such errors. A comparison with the results of an experiment on surface diffusion shows that heavy sputtering increases the surface diffusion coefficient by 2 to 3 orders of magnitude.     

Nanometer-scale objects of deposition and sputtering

Recent theoretical and experimental works involving the study of processes of interaction of accelerated particles with solid surfaces on the nanometer-scale level are discussed. In this survey, considerable attention is given to computer simulation research. This survey contains data in the following fields: bombardment of solid surfaces by a stream of energy clusters, cluster emission during sputtering, and sputtering of nanodimensional targets.     

Low energy ion impact phenomena on single crystal surfaces

The dynamics of a solid bombarded by a 600 eV Ar⁺ ion have been studied classically by computer simulation. The model uses a crystallite of about 250 atoms described by pair potentials derived from elastic constants and which reproduce the surface binding energy of the solid. The relative calculated yield of secondary atom emission from the three low index faces of Cu follow the previously determined experimental order (111) > (100) > (110). We find major differences in the sputtering mechanisms for these faces. On (110), the impacted atom is ejected most frequently, while on (111) and (100) it almost never leaves the solid. We report the energy distribution of the sputtered particles for each face. The simulation successfully predicts the shape of the curve including the low energy maximum which is observed experimentally near 2 eV. In addition our model shows that many low energy atoms attempt to leave the crystal but are subsequently trapped to the solid at large distances from their original sites. This mechanism of radiation enhanced diffusion inevitably occurs in conjunction with sputtering or any other heavy secondary particle emission or scattering process.     

Calculation of ion and fast atom contributions to the sputtering non-uniformity of the target with a surface relief in glow discharge

The energy spectra of ion and fast atom flows at the target with a periodical surface relief of small amplitude in glow discharge are calculated. Distributions of the effective sputtering yield of the target and the sputtered atom flow density along its surface are found. It is shown that contributions of the fast atom flow non-uniformity in them are much less than that of the ion flow non-uniformity and may not be taken into account in the simulation of target sputtering in glow discharge when its surface relief element dimensions are small in comparison with the discharge cathode sheath length.     

采用壳层效应屏蔽长度Monte Carlo方法计算溅射产额

使用ACAT模拟程序计算了不同离子碰撞在单原子材料上的溅射产额.采用山村等人提出的考虑壳层效应的理论屏蔽长度,原子间作用势用Moliére势.并将计算结果与实验数据和山村等的经验公式进行了比较.     

Computer simulation of two-component target sputtering

The TRIM SP computer simulation program, which is based on the binary collision approximation, is applied to sputtering of two component targets. The topics discussed in this paper are: contribution of different processes leading to sputtering, total and partial sputtering yields, surface compositions at stationary conditions, sputtering of isotopic mixtures, angular and energy distributions and the escape depth of sputtered particles. Targets investigated are TaC, WC, TiC, TiD₂, and B (as an isotope mixture), bombarded by the noble gas ions and D (in the case of TiD₂). Comparison with experimental data and calculated results show good agreement demonstrating that collisional effects are sufficient to describe the experimental data in the examples investigated.     

The sputtering mechanism for low-energy light ions

The computer simulation program MARLOWE which follows the trajectories of energetic ions and recoiling target atoms in solids has been used to calculate sputtering yields for low energy (0.1–10keV) light ions (H, D, T,⁴He). Recoil energy densities were calculated for comparison with analytical theories. The sputtering yields obtained for amorphous Fe agree within a factor of two with experimentally measured values for polycrystalline stainless steel, while the calculated yields for protons on amorphous molybdenum are more than twice the experimental values on polycrystalline material. The calculations show that in the parameter range investigated, ions backscattered in the solid contribute a major part to sputtering. This result confirms earlier calculations of the threshold energy for sputtering which are in agreement with recent measurements. Operated for the United States Department of Energy by the Union Carbide Corporation.     

Optical characterization and laser damage of fused silica optics after ion beam sputtering

The sputtering process of fused silica bombarded by Ar ion beam is simulated with the SRIM software. The effects of ion beam energy and incident angle on sputtering yield and surface damage are computed. Since ion beam sputtering will result in defects in fused silica, such as E′ color centers and other lattice defects and probably Argon bubbles, the optimized sputtering energy is selected below 1 keV so that the projected range of Ar ions is less than 10 Å. The experimental results show that the scratches in subsurface of fused silica can be smoothed obviously and better surface can be obtained as the optimized parameters are used for ion beam sputtering. The laser induced damage threshold of fused silica increases by about 18% after ion beam sputtering.     

Calculations of the level of primary radiation defects (displacements per atom) taking into account surface sputtering

The results of analytical estimates and computer simulations of the primary radiation damage level in the number of displacements per atom (dpa) in solids are presented and compared, taking into account the material sputtering under ion bombardment. Calculations were performed for the bombardment of carbon-based materials by Ar⁺, Ne⁺, and N⁺ ions with energies of 2?C30 keV, when considerable ion-induced changes in the material??s structure are observed. A comparison shows the close fit of the analytical and computer calculations.     

GaP薄膜的射频磁控溅射沉积及其计算机模拟

以GaP为靶材采用射频磁控溅射法制备GaP红外光学薄膜，通过保持Ar Ⅰ 750nm发射光谱线强度不变获得了不同工艺参数，并对沉积过程进行了计算机模拟.功率较小、气压较大时，Ga和P的溅射率、输运效率及沉积到衬底时的能量均较小，Ga的溅射率及输运效率均大于P的，使薄膜沉积速率较低、薄膜中Ga的含量大于P的，GaP薄膜产生较大吸收.功率较大、气压较小时，Ga和P的溅射率、输运效率及沉积到衬底时的能量均增大，Ga的溅射率大于P的、但其输运效率小于P的，使GaP薄膜的沉积速率增大、薄膜中Ga与P的含量接近化学计量比，GaP薄膜的吸收降低，因此有利于制备厚度较大的GaP薄膜. 关键词： GaP 薄膜 射频磁控溅射 计算机模拟